The invention relates to a process for proportioning thick matter such as a viscous material which is delivered under pressure from a supply, is then proportioned and is applied by way of a controlled outlet valve to an application point and to an arrangement for proportioning viscous material, consisting of at least one storage container and a feed pump which is connected with a proportional metering device by way of a feed pipe as well as of a controlled outlet valve.
In many fields of technology, particularly in the automated manufacturing of motor vehicle bodies, it is required to apply viscous material, particularly sealing agents and adhesives, to certain surfaces. For example, in the case of motor vehicles, threads or thin strips of sealing agents or adhesives are applied along edges, lock seams or seams of motor vehicle body parts.
This application can take place manually as well as by programmed automatic manipulating machines, as described, for example, in German Patent document DE-C 32 36 647.
In practice, considerable difficulties with such application operations are encountered because, on the one hand, a fast manufacturing is desired and, on the other hand, a sufficient application, which is as uniform as possible, of the viscous material is required. In this case, it should be taken into account that the same types of viscous material will often have different flow properties because of a different viscosity, specifically also when this is viscous material from the same manufacturing batch which is processed within a very short time. This considerably impairs the uniform delivery of the viscous material or a delivery which can be changed in a proportioned manner.
Despite large expenditures, the known arrangements which have very sensitive control circuits do not constantly achieve the desired result because of their high susceptibility.
There is therefore needed a process and an arrangement by which the flow properties of viscous material are influenced in a simple manner such that, when the nozzle openings have the same sizes, the same quantities can always be delivered per unit of time.
According to the invention, these needs are met by a process and apparatus for proportioning viscous material which is delivered under pressure from a supply, is then proportioned and is applied by way of a controlled outlet valve to an application point. The proportioning takes place directly in front of the outlet valve separately for each quantity to be applied. Because of the fact that the outlet valve and the proportioning are directly connected with one another, it is possible to proportion immediately before the application and to then discharge directly. This will eliminate the previous long flow paths between the proportioning and the outlet valve which have led to inaccuracies of the outflow rate per unit of time. This also eliminates the additional feed pipes. Another advantage is the fact that the viscous material to be discharged can be sufficiently mixed or sheared immediately during the filling of the proportioning device.
A reinforcement of the mixing device or the shearing of the viscous material is achieved by providing a mixing section, for example, a static mixer tube can be installed in the inlet of the proportioning device.
In a further particularly advantageous embodiment of the process the proportioning takes place by means of a purely volumetric control in that, in the case of deviations in the application quantity during one discharge operation, the subsequent discharge operation is controlled to a desired value. This embodiment minimizes the control expenditures and nevertheless achieves excellent results.
By means of the further development, viscosity differences caused by temperature changes are avoided.
A still further development has the advantage that the previously known switching valve at the outlet of the proportional metering device can be eliminated and the outlet valve can be connected directly to the delivery chamber of the proportional metering device. This further minimizes the control expenditures.
Another development according to the invention achieves the advantage that the viscous material is continuously delivered into the proportional metering device so that viscous material does not have to be stored there for extensive waiting periods which, in turn, would result in differences in viscosity. This ensures that there is sufficient mixing and shearing immediately before the application of the viscous material.
In a further development according to the invention, the differences in viscosity resulting from variations in temperature are avoided. In this case, it is not required to temper the whole feed pipe between the storage container and the proportional metering device. It is sufficient to temper thirty (30) times the application volume. "Tempering" in this case is the achieving of a constant temperature; that is, a heating or cooling depending on the environmental influences.
The further development according to the invention describes a preferred development for the tempering. In this case, it was also found to be effective to include the proportional metering device and the outlet valve.
The present invention describes a simple possibility of providing a volumetric control.
By means of the pressure relief of the flow rates during production stoppages, the thixotropy can be kept constant.
By further developing the invention, the mixing and flexing of the viscous material to be proportioned will be promoted further.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.